For want of a nail the shoe was lost; for want of a shoe the horse ...
for want of a nail
proverb Due to a minor inconvenience or mishap, (something much worse has happened). The full proverb is “For want of a nail the shoe was lost. For want of a shoe the horse was lost. For want of a horse the rider was lost. For want of a rider the battle was lost. For want of a battle the kingdom was lost. And all for the want of a horseshoe nail.” If only you'd taken your car in for an oil change when you were supposed to, this emergency trip to the mechanic could have been avoided. Ah, for want of a nail.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
For want of a nail the shoe was lost; for want of a shoe the horse was lost; and for want of a horse the man was lost.
Prov. Overlooking small details can have disastrous consequences. (You can quote any of the sentences in this proverb by themselves.) Jill: I don't think we need to check our bicycle tires before we go for our ride. Jane: I disagree. For want of a nail the shoe was lost. Before we began the hike into the mountains, we checked our equipment painstakingly, remembering that for want of a horse the man was lost.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.